1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device and a driving method thereof. Another embodiment of the present invention relates to an electronic device.
Note that one embodiment of the present invention is not limited to the above technical field. One embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Furthermore, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. It can be said that a display device (e.g., a liquid crystal display device and a light-emitting display device), a projection device, a lighting device, an electro-optical device, a power storage device, a memory device, a semiconductor circuit, an imaging device, an electronic device, and the like include a semiconductor device in some cases.
2. Description of the Related Art
A technique in which a transistor is formed using a semiconductor material has attracted attention. The transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device (also simply referred to as a display device). As semiconductor materials applicable to the transistor, silicon-based semiconductor materials have been widely used, but oxide semiconductors have been attracting attention as alternative materials.
Patent Document 1 discloses an example in which a transistor including an oxide semiconductor in a channel formation region (hereinafter referred to as an oxide semiconductor transistor) is used in a dynamic random access memory (DRAM). The oxide semiconductor transistor has extremely low current flowing between a source and a drain when the transistor is in an off-state (off-state current); thus, a low-power DRAM having a low refresh frequency can be formed.
Patent Document 2 discloses a nonvolatile memory including an oxide semiconductor transistor. Unlike the flash memory, the nonvolatile memory has unlimited cycling capability, can easily operate at high speed, and consumes less power.
Patent Document 2 discloses an example in which an oxide semiconductor transistor has a second gate electrode to control the threshold voltage of the transistor so that the off-state current of the transistor is lowered.
Patent Documents 2 and 3 each disclose a structure example of a circuit for driving the second gate.